U.S. patent application number 14/114779 was filed with the patent office on 2014-03-13 for battery can for storage battery.
This patent application is currently assigned to NIPPON STEEL & SUMITOMO METAL CORPORATION. The applicant listed for this patent is Kohji Miyoshi, Teruaki Yamada. Invention is credited to Kohji Miyoshi, Teruaki Yamada.
Application Number | 20140072841 14/114779 |
Document ID | / |
Family ID | 47139156 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140072841 |
Kind Code |
A1 |
Yamada; Teruaki ; et
al. |
March 13, 2014 |
BATTERY CAN FOR STORAGE BATTERY
Abstract
Disclosed is a battery can for a storage battery, provided with
a safety valve having a first and a second score groove portion is
provided to inner and outer surface of can bottom, can body, or can
lid. The first and the second score groove portion face each other,
and have a first and a second score groove bottom portion, which
have a radius of curvature R, respectively. The R is more than 0.20
mm and less than 1.20 mm, and a distance between the bottom
portions is 0.045 to 0.150 mm. The portion, which has the safety
valve, is constituted by a plated steel sheet having a steel sheet
portion of C content is less than 0.040 mass %, S content is less
than 0.020 mass %, and tensile strength TS is less than 400 MPa,
and a plate layer formed on a surface of the steel sheet
portion.
Inventors: |
Yamada; Teruaki; (Tokyo,
JP) ; Miyoshi; Kohji; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yamada; Teruaki
Miyoshi; Kohji |
Tokyo
Tokyo |
|
JP
JP |
|
|
Assignee: |
NIPPON STEEL & SUMITOMO METAL
CORPORATION
Tokyo
JP
|
Family ID: |
47139156 |
Appl. No.: |
14/114779 |
Filed: |
May 1, 2012 |
PCT Filed: |
May 1, 2012 |
PCT NO: |
PCT/JP2012/061545 |
371 Date: |
October 30, 2013 |
Current U.S.
Class: |
429/53 |
Current CPC
Class: |
B32B 15/015 20130101;
H01M 2/1241 20130101; C25D 5/48 20130101; C25D 7/00 20130101; H01M
2/0404 20130101; C22C 38/004 20130101; H01M 2/1229 20130101; C22C
38/04 20130101; H01M 2/024 20130101; Y02E 60/10 20130101; C22C
38/12 20130101; H01M 2/043 20130101; C22C 38/002 20130101; C22C
38/001 20130101; C22C 38/14 20130101; C22C 38/06 20130101; C22C
38/02 20130101 |
Class at
Publication: |
429/53 |
International
Class: |
H01M 2/12 20060101
H01M002/12; H01M 2/02 20060101 H01M002/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 9, 2011 |
JP |
2011-104422 |
Claims
1. A battery can for a storage battery, comprising: a tubular can
body portion having a first end and a second end; a can bottom
portion that is continuous to the can body portion so as to cover
the first end of the can body portion; and a can lid portion that
is continuous to the can body portion so as to cover the second end
of the can body portion when constituting a battery, wherein a
safety valve having a first score groove portion and a second score
groove portion that are opposite to each other in a cross-sectional
view in a sheet thickness direction is provided to an inner surface
and an outer surface of any one of the can bottom portion, the can
body portion, and the can lid portion, when viewed from a
cross-section that is perpendicular to an extension direction of
the first score groove portion, the first score groove portion and
the second score groove portion have a first score groove bottom
portion and a second score groove bottom portion, which have a
radius of curvature R and a relative clearance of 0.045 mm to 0.150
mm, respectively, the radius of curvature R is more than 0.20 mm
and is equal to or less than 1.20 mm, and any one of the can bottom
portion, the can body portion, and the can lid portion, which has
the safety valve, is constituted by a plated steel sheet having a
steel sheet portion in which the amount of C is limited to 0.040%
by mass or less and the amount of S is limited to 0.020% by mass or
less, and a tensile strength TS is 400 MPa or less, and a plate
layer formed on the steel sheet portion.
2. The battery can for a storage battery according to claim 1,
wherein the plated steel sheet is subjected to score processing by
a press forming method.
3. The battery can for a storage battery according to claim 1,
wherein after the steel sheet portion is subjected to the score
processing by the press forming method, the plated layer is formed
on a surface of the steel sheet portion.
4. A battery can for a storage battery, comprising: a tubular can
body portion having a first end and a second end; a can bottom
portion that is continuous to the can body portion so as to cover
the first end of the can body portion; and a can lid portion that
is continuous to the can body portion so as to cover the second end
of the can body portion when constituting a battery, wherein a
safety valve having a first score groove portion and a second score
groove portion that are opposite to each other in a cross-sectional
view in a sheet thickness direction is provided to an inner surface
and an outer surface of any one of the can bottom portion, the can
body portion, and the can lid portion, when viewed from a
cross-section that is perpendicular to an extension direction of
the first score groove portion, the first score groove portion and
the second score groove portion have a first score groove bottom
portion and a second score groove bottom portion, which have a
radius of curvature R and a relative clearance of 0.055 mm to 0.150
mm, respectively, the radius of curvature R is 0.30 mm to 1.20 mm,
and any one of the can bottom portion, the can body portion, and
the can lid portion, which has the safety valve, is constituted by
a plated steel sheet having a steel sheet portion in which the
amount of C is limited to 0.100% by mass or less and the amount of
S is limited to 0.030% by mass or less, and a tensile strength TS
is 400 MPa or less, and a plate layer formed on the steel sheet
portion.
5. The battery can for a storage battery according to claim 4,
wherein the plated steel sheet is subjected to score processing by
a press forming method.
6. The battery can for a storage battery according to claim 4,
wherein after the steel sheet portion is subjected to the score
processing by the press forming method, the plated layer is formed
on a surface of the steel sheet portion.
7. The battery can for a storage battery according to claim 1,
wherein the plated layer is Ni plating.
8. The battery can for a storage battery according to claim 1,
wherein the radius of curvature R is 0.30 mm to 1.20 mm.
9. The battery can for a storage battery according to claim 8,
wherein the plated layer is Ni plating.
10. A battery can for a storage battery, comprising: a tubular can
body portion having a first end and a second end; a can bottom
portion that is continuous to the can body portion so as to cover
the first end of the can body portion; and a can lid portion that
is continuous to the can body portion so as to cover the second end
of the can body portion when constituting a battery, wherein a
safety valve having a first score groove portion and a second score
groove portion that are opposite to each other in a cross-sectional
view in a sheet thickness direction is provided to an inner surface
and an outer surface of any one of the can bottom portion, the can
body portion, and the can lid portion, when viewed from a
cross-section that is perpendicular to an extension direction of
the first score groove portion, the first score groove portion and
the second score groove portion have a first score groove bottom
portion and a second score groove bottom portion, which have a
radius of curvature R and a relative clearance of 0.045 mm to 0.150
mm, respectively, the radius of curvature R is more than 0.20 mm
and is equal to or less than 1.20 mm, and any one of the can bottom
portion, the can body portion, and the can lid portion, which has
the safety valve, is constituted by a stainless steel sheet in
which the amount of C is limited to 0.040% by mass or less and the
amount of S is limited to 0.020% by mass or less, and a tensile
strength TS is 400 MPa or less.
11. The battery can for a storage battery according to claim 10,
wherein the stainless steel sheet is subjected to score processing
by a press forming method.
12. The battery can for a storage battery according to claim 10,
wherein the radius of curvature R is 0.30 mm to 1.20 mm.
13. The battery can for a storage battery according to claim 2,
wherein the plated layer is Ni plating.
14. The battery can for a storage battery according to claim 3,
wherein the plated layer is Ni plating.
15. The battery can for a storage battery according to claim 4,
wherein the plated layer is Ni plating.
16. The battery can for a storage battery according to claim 5,
wherein the plated layer is Ni plating.
17. The battery can for a storage battery according to claim 6,
wherein the plated layer is Ni plating.
18. The battery can for a storage battery according to claim 2,
wherein the radius of curvature R is 0.30 mm to 1.20 mm.
19. The battery can for a storage battery according to claim 3,
wherein the radius of curvature R is 0.30 mm to 1.20 mm.
20. The battery can for a storage battery according to claim 11,
wherein the radius of curvature R is 0.30 mm to 1.20 mm.
Description
TECHNICAL FIELD
[0001] The present invention relates to a battery can for a storage
battery, which is provided with a score groove type safety valve.
Particularly, the battery can for a storage battery is suitably
used for an industrial use and an in-vehicle use.
[0002] Priority is claimed on Japanese Patent Application No.
2011-104422, filed on May 9, 2011, the content of which is
incorporated herein by reference.
BACKGROUND ART
[0003] Recently, an assembled battery for an industrial use and an
in-vehicle use, which uses a high-output battery, has been
spreading quickly. In the assembled battery that is used for these
purposes, there is a demand for continuing high performance
(battery characteristics) over a long period of 10 to 15 years.
Accordingly, there is a demand for individual batteries used in the
assembled battery to have, for example, the following
performance.
[0004] First, even when the assembled battery is used under harsh
conditions over a long period of 10 to 15 years, there is a demand
that deterioration in performance of an individual battery be
small. Furthermore, the performance of the assembled battery in
which a number of batteries are connected is greatly affected by
battery performance of one battery having the lowest performance in
the assembled battery. Thus, a variance in the battery performance
of the individual batteries, which occurs due to deterioration of
the battery performance during a long period of use, is demanded to
be small. In addition, there is a demand for the individual
batteries to secure satisfactory corrosion resistance for a long
period of time.
[0005] As a technology in the related art, for example, the
following Patent Documents 1 to 5 are exemplary examples.
[0006] Patent Document 1 discloses a thionyl chloride lithium
battery that is used as a battery for an electronic apparatus. In
this thionyl chloride lithium battery, a thin groove portion is
provided at a part of a battery lid or a battery case, and a
trapezoidal groove (score) on an inner side of a can is shown as a
thin groove portion. In Patent Document 1, in a case where inner
pressure increases during abnormality in a battery, the thin groove
portion is allowed to be ruptured at low pressure, whereby the thin
groove portion is used as a safety valve.
[0007] Patent Document 2 discloses a square-type sealed battery
having a thin groove portion along a width direction of a sealing
lid. The thin groove portion has a V-shaped cross-section, and is
formed by press working.
[0008] Patent Document 3 discloses a cylindrical storage battery in
which a rupture valve is formed in a diaphragm that is inversed due
to an increase in inner pressure and blocks a current. In the
cylindrical storage battery, a groove, which has a V-shaped
cross-section and which is constituted by a combination of a
circular curve positioned at a surface opposite to a surface of the
diaphragm to which the inner pressure is applied, and a straight
line of which one end intersects the circular curve and the other
end is located on an outer periphery side of the diaphragm in
relation to the circular curve, is formed as the rupture valve. In
addition, in the cylindrical storage battery, a groove having a
U-shaped cross-section is formed in a surface of the diaphragm to
which the inner pressure is applied and which corresponds to the
position at which the groove having the V-shaped cross-section is
formed. In the straight groove, the depth on the other end side is
shallower than the depth on the one end side. Furthermore, the
depth of the groove having the U-shaped cross-section is shallower
than the depth of the groove having the V-shaped cross-section.
[0009] Patent Document 4 and Patent Document 5 disclose an
easy-open can lid that is opened by rupturing an opening formed in
a can lid of a can body so the contents can be taken out, and a
production method thereof. The easy-open can lid is different from
the battery can in the technical field, and is used as a can lid
for a beverage can or a food can. A resin-coated steel sheet is
applied as a material of the can lid.
[0010] In the assembled battery (storage battery) for industrial
use and in-vehicle use, which uses a high-output battery, there is
a demand for a battery can capable of satisfying the
characteristics necessary for the battery. The present inventors
have found that it is necessary to consider the following
performance for the battery can.
[0011] For example, performance stability of a safety valve during
a long period of use is necessary for the battery can. Factors
deteriorating the performance stability are as follows: a pressure
variation in a battery can due to repetition of charging and
discharging (that is, fatigue of the safety valve), and an effect
by the contents such as an electrolytic solution (that is,
corrosion of the safety valve). In addition, with regard to an
individual battery can when being used as an assembled battery, it
is necessary for the battery can to have a small variance in a
valve opening pressure of the safety valve (that is, uniformity in
performance of the safety valve).
[0012] However, the thionyl chloride lithium battery that is a
primary battery does not perform charging and discharging, and thus
in the battery can disclosed in Patent Document 1, it is not
necessary to consider fatigue resistance of the safety valve. In
addition, the primary battery for an electronic apparatus hardly
ever constitutes an assembled battery, and thus a demand for
uniformity in performance of the safety valve with respect to a
plurality of batteries is not so high. Accordingly, in Patent
Document 1, an expensive stainless steel sheet or nickel steel
sheet, which has high corrosion resistance, is used, and a
trapezoidal score groove is formed in one surface (inner surface of
a battery) of the sheet in such a manner that the valve opening
pressure may be adjusted by changing a width of the score
groove.
[0013] In addition, in the square-type battery for portable
apparatuses, which is disclosed in Patent Document 2, a life cycle
of the apparatuses that are used is short, and is frequently
shorter than 10 years, and thus a demand for the fatigue resistance
with respect to the safety valve or uniformity in performance of
the safety valve with respect to a plurality of batteries is not so
high. Accordingly, in Patent Document 2, a V-shaped thin groove
portion is used as the safety valve in order to progress a crack
from the thin groove portion.
[0014] In Patent Document 3, the storage battery has a battery can
in which a rupture valve is ruptured after inversion of the
diaphragm, and to realize this function, a rupture valve is
configured by a groove having a V-shaped cross-section, and a
U-shaped groove which is opposite to the groove having a V-shaped
cross-section. Accordingly, in the storage battery disclosed in
Patent Document 3, a demand for the fatigue resistance with respect
to the rupture valve or uniformity in performance of the safety
valve with respect to a plurality of batteries is not so high.
[0015] In the easy-open can (hereinafter, referred to as an EOE
can) disclosed in Patent Document 4 and Patent Document 5, a
structure of the can lid is different from that of a portion of the
battery can which is provided with a safety valve, and
particularly, a can opening mechanism itself is completely
different from a mechanism of the battery can provided with the
safety valve.
[0016] That is, in Patent Document 4 and Patent Document 5, a large
force is caused to operate on a local point of a score contour by a
tab that functions as a lever, the one local point of the score
contour is opened, and then the majority of the score contour is
opened by pushing force of the tab. In this manner, in Patent
Document 4, a can lid having a mechanical opening function is used.
Accordingly, with regard to a mechanical function of opening a can
and can opening characteristics that are necessary, the can lid is
basically different from the battery can provided with the safety
valve.
[0017] A difference between a can opening technology in the field
of beverage can, and a valve opening technology of the battery can
will be described below.
[0018] The safety valve of the battery can is reliably opened at a
point of time at which inner pressure generated during charging
reaches a predetermined designed inner pressure, and the battery
can itself is prevented from being ruptured. When the designed
inner pressure of the safety valve is too high, the battery inner
pressure increases too much, and thus the battery can is apt to be
ruptured. On the other hand, when the designed inner pressure of
the safety valve is too low, the safety valve is opened during
charging, and thus an assembled battery itself is broken.
Accordingly, it is necessary to limit the upper limit of an amount
of charge, and thus the performance of the assembled battery is
greatly limited.
[0019] On the other hand, the beverage can uses a method (a
technical field in which a can opening mechanism is completely
different from a mechanism of the safety valve of the battery can)
in which force is focused on one point of the score portion by a
component called a tab functioning as a lever to allow large force
to operate so as to open the can. Accordingly, performance
necessary for this method (that is, performance of the beverage
can) includes durability against an impact, easiness of can
opening, and mass productivity. With regard to the durability
against an impact, for example, even when a can into which contents
are put is dropped several times at a height of approximately 1 m,
it is necessary for the durability to have a level at which a score
portion is not opened by deformation of the can due to the dropping
and the contents do not flow out. This level is sufficiently lower
than a level necessary for the battery can, and thus a remaining
score thickness (Min value) may be made to be small to the limit of
a level necessary for the durability against an impact. In
addition, with regard to the easiness of the can opening, it is
necessary to set the upper limit of can opening power to a
remaining score thickness level capable of being opened by the tip
of a finger of human. The can opening power has a variation
depending on kinds of cans, makers, and the like, and has a large
margin within a setting range of the can opening power (a technical
field having a margin for the setting of the remaining score
thickness). Accordingly, in the beverage can, the can opening power
may vary in an individual beverage can, and it is not necessary to
increase the processing accuracy to a certain degree of the battery
can to increase mass productivity.
[0020] In addition, with regard to the safety valve of the battery
can, it is necessary for the score portion of the safety valve not
to be fatigue-broken under conditions in which large inner pressure
is repetitively applied to the battery can at all times over 10 to
15 years, and it is necessary for the safety valve to be opened at
a point of time at which inner pressure set as valve opening
pressure is loaded. On the other hand, in the beverage can, the
repetitive load itself is not present. Accordingly, the technical
field of the beverage can is a technical field in which it is not
necessary to consider fatigue strength to which the present
inventors give attention.
[0021] Accordingly, the technology of the beverage can does not
have the same technical idea as the battery can which endures a
repetitive stress load over a long period of time, and which is
reliably opened at a point of time at which a predetermined loaded
inner pressure is applied.
[0022] Also, as disclosed in Patent Document 5, in a case where the
bottom of the score groove has a curvature, large can-opening-power
is necessary, and thus can opening properties decrease.
Accordingly, in this case, it is necessary to extremely decrease
the remaining score thickness.
[0023] In addition, in the safety valve of the battery can, it is
necessary for the valve opening pressure itself not to be too much
lower than a set value, and not to be too much higher than the set
value, that is, it is necessary for a variance in an absolute value
of the valve opening pressure of a number of battery cans to be
small. Furthermore, since an assembled battery is designed in such
a manner that the valve opening pressure is common to all of
assembled batteries that are produced, it is necessary for
individual battery cans used in all of the assembled batteries to
have a small variance in the valve opening pressure of the safety
valve of the battery can. As mentioned above, with regard to the
battery can, accuracy (reproducibility) of the safety valve of the
individual battery can is a very important technical field.
However, the beverage can belongs to a technical field having no
such technical idea.
[0024] As mentioned above, the valve opening technology of the
battery can is completely different from the can opening technology
of the beverage can.
PRIOR ART DOCUMENT
Patent Document
[0025] [Patent Document 1] Japanese Unexamined Patent Application,
First Publication No. S59-79965 [0026] [Patent Document 2] Japanese
Registered Utility Model No. 2585726 [0027] [Patent Document 3]
Japanese Patent No. 4346637 [0028] [Patent Document 4] Japanese
Patent No. 3893198 [0029] [Patent Document 5] Japanese Unexamined
Patent Application, First Publication No. 2000-233247
DISCLOSURE OF THE INVENTION
Problem that the Invention is to Solve
[0030] The invention is to provide a battery can for a storage
battery (particularly, for an industrial use and an in-vehicle use)
which is provided with a safety valve in which a variance in valve
opening pressure of a score groove portion of an individual battery
can is small, and the valve opening pressure of the score groove
portion scarcely decreases by deterioration of the battery can with
the passage of time (for example, over 10 to 15 years) due to
fatigue or corrosion. Accordingly, the problem of the battery can
for a storage battery is completely different from the technical
problem disclosed in the prior art documents.
Means for Solving the Problems
[0031] To provide a battery can in which the above-described
problem is solved, the present inventors have made various
examinations on a mechanical function of stably opening the battery
can, and valve opening characteristics necessary for valve opening,
and they have accomplished the invention. The gist of the invention
is as follows.
[0032] (1) According to a first aspect of the invention, there is
provided a battery can for a storage battery. The battery can
includes a tubular can body portion having a first end and a second
end, a can bottom portion that is continuous to the can body
portion so as to cover the first end of the can body portion, and a
can lid portion that is continuous to the can body portion so as to
cover the second end of the can body portion when constituting a
battery. A safety valve having a first score groove portion and a
second score groove portion that are opposite to each other in a
cross-sectional view in a sheet thickness direction is provided to
an inner surface and an outer surface of any one of the can bottom
portion, the can body portion, and the can lid portion. When viewed
from a cross-section that is perpendicular to an extension
direction of the first score groove portion, the first score groove
portion and the second score groove portion have a first score
groove bottom portion and a second score groove bottom portion,
which have a radius of curvature R and a relative clearance of
0.045 mm to 0.150 mm, respectively. The radius of curvature R is
more than 0.20 mm and is equal to or less than 1.20 mm. Any one of
the can bottom portion, the can body portion, and the can lid
portion, which has the safety valve, is constituted by a plated
steel sheet having a steel sheet portion in which the content of C
is limited to 0.040% by mass or less and the content of S is
limited to 0.020% by mass or less, and tensile strength TS is 400
MPa or less, and a plate layer formed on the steel sheet
portion.
[0033] (2) In the battery can for a storage battery according to
(1), the plated steel sheet may be subjected to score processing by
a press forming method.
[0034] (3) In the battery can for a storage battery according to
(1), after the steel sheet portion is subjected to the score
processing by the press forming method, the plated layer may be
formed on a surface of the steel sheet portion.
[0035] (4) According to a second aspect of the invention, there is
provided a battery can for a storage battery. The battery can
includes a tubular can body portion having a first end and a second
end, a can bottom portion that is continuous to the can body
portion so as to cover the first end of the can body portion, and a
can lid portion that is continuous to the can body portion so as to
cover the second end of the can body portion when constituting a
battery. A safety valve having a first score groove portion and a
second score groove portion that are opposite to each other in a
cross-sectional view in a sheet thickness direction is provided to
an inner surface and an outer surface of any one of the can bottom
portion, the can body portion, and the can lid portion. When viewed
from a cross-section that is perpendicular to an extension
direction of the first score groove portion, the first score groove
portion and the second score groove portion have a first score
groove bottom portion and a second score groove bottom portion,
which have a radius of curvature R and a relative clearance of
0.055 mm to 0.150 mm, respectively. The radius of curvature R is
0.30 mm to 1.20 mm. Any one of the can bottom portion, the can body
portion, and the can lid portion, which has the safety valve, is
constituted by a plated steel sheet having a steel sheet portion in
which the amount of C is limited to 0.100% by mass or less and the
amount of S is limited to 0.030% by mass or less, and tensile
strength TS is 400 MPa or less, and a plate layer formed on the
steel sheet portion.
[0036] (5) In the battery can for a storage battery according to
(4), the plated steel sheet may be subjected to score processing by
a press forming method.
[0037] (6) In the battery can for a storage battery according to
(5), after the steel sheet portion is subjected to the score
processing by the press forming method, the plated layer may be
formed on a surface of the steel sheet portion.
[0038] (7) In the battery can for a storage battery according to
any one of (1) to (6), the plated layer may be Ni plating.
[0039] (8) In the battery can for a storage battery according to
any one of (1) to (3), the radius of curvature R may be 0.30 mm to
1.20 mm.
[0040] (9) In the battery can for a storage battery according to
(8), the plated layer may be Ni plating.
[0041] (10) According to a third aspect of the invention, there is
provided a battery can for a storage battery. The battery can
includes a tubular can body portion having a first end and a second
end, a can bottom portion that is continuous to the can body
portion so as to cover the first end of the can body portion, and a
can lid portion that is continuous to the can body portion so as to
cover the second end of the can body portion when constituting a
battery. A safety valve having a first score groove portion and a
second score groove portion that are opposite to each other in a
cross-sectional view in a sheet thickness direction is provided to
an inner surface and an outer surface of any one of the can bottom
portion, the can body portion, and the can lid portion. When viewed
from a cross-section that is perpendicular to an extension
direction of the first score groove portion, the first score groove
portion and the second score groove portion have a first score
groove bottom portion and a second score groove bottom portion,
which have a radius of curvature R and a relative clearance of
0.045 mm to 0.150 mm, respectively. The radius of curvature R is
more than 0.20 mm and is equal to or less than 1.20 mm. Any one of
the can bottom portion, the can body portion, and the can lid
portion, which has the safety valve, is constituted by a stainless
steel sheet in which the amount of C is limited to 0.040% by mass
or less and the amount of S is limited to 0.020% by mass or less,
and tensile strength TS is 400 MPa or less.
[0042] (11) In the battery can for a storage battery according to
(10), the stainless steel sheet may be subjected to score
processing by a press forming method.
[0043] (12) In the battery can for a storage battery according to
(10) or (11), the radius of curvature R may be 0.30 mm to 1.20
mm.
Advantage of the Invention
[0044] According to the aspects of the invention, it is possible to
provide a battery can for a storage battery which is provided with
a safety valve in which a variance in valve opening pressure of a
score groove portion of an individual battery can is small, and the
valve opening pressure of the score groove portion scarcely
decreases by deterioration of the battery can with the passage of
time (for example, over 10 to 15 years) due to fatigue or
corrosion. Accordingly, an industrial value is significantly
high.
[0045] Particularly, in the battery can for a storage battery
according to (1) to (12), a decrease in the valve opening pressure
of the score groove portion by fatigue caused by a repetitive
variation in inner pressure (repetitive stress) which is loaded on
the battery can over a long period of time (10 to 15 years) may be
effectively suppressed.
[0046] In addition, in the battery can for a storage battery
according to (1) to (9), a decrease in the valve opening pressure
of the score groove portion, which is caused by pitting or the like
of the score groove portion in the anticorrosive plated steel sheet
having a plate layer such as Ni plating, may be effectively
suppressed.
BRIEF DESCRIPTION OF THE DRAWING
[0047] FIG. 1 is a graph illustrating a relationship between a
radius of curvature R and valve opening pressure.
[0048] FIG. 2 is a graph illustrating a relationship between the
radius of curvature R and an index of soundness of a Ni plated
layer (average elongation rate of the Ni plated layer).
[0049] FIG. 3A is a schematic perspective diagram illustrating a
battery can according to an embodiment of the invention.
[0050] FIG. 3B is a schematic perspective diagram illustrating a
battery can according to a modification example of the
embodiment.
[0051] FIG. 3C is a schematic perspective diagram illustrating a
battery can according to a modification example of the
embodiment.
[0052] FIG. 3D is a schematic perspective diagram illustrating a
battery can according to a modification example of the
embodiment.
[0053] FIG. 3E is a schematic perspective diagram illustrating a
battery can according to a modification example of the
embodiment.
[0054] FIG. 3F is a schematic perspective diagram illustrating a
battery can according to a modification example of the
embodiment.
[0055] FIG. 4 is a schematic longitudinal cross-sectional diagram
of the battery can according to the embodiment.
[0056] FIG. 5A is a schematic partial cross-sectional diagram
illustrating an example of a score groove portion of the battery
can according to an embodiment of the invention.
[0057] FIG. 5B is a schematic partial cross-sectional diagram
illustrating an example of the score groove portion of the battery
can according to the embodiment of the invention.
[0058] FIG. 6A is an explanatory diagram illustrating a radius of
curvature R and a remaining score thickness d in FIG. 5A.
[0059] FIG. 6B is an explanatory diagram illustrating a radius of
curvature R, a remaining score thickness d, and a groove opening
degree .theta.' in FIG. 5B.
[0060] FIG. 7A is an explanatory diagram illustrating stress
concentration in a case of forming a trapezoidal score groove by
press working.
[0061] FIG. 7B is an explanatory diagram illustrating stress
dispersion in a case of forming an arc-shaped score groove by the
press working.
BEST MODE FOR CARRYING OUT THE INVENTION
[0062] Hereinafter, the invention will be described in detail.
[0063] The present inventors have carried out an examination on a
score groove type safety valve of a battery can for a storage
battery (particularly, for an industrial use and an in-vehicle use)
in which a variance in valve opening pressure of a score groove
portion of an individual battery can is small, and the valve
opening pressure of the score groove portion scarcely decreases by
deterioration of the battery can with the passage of time due to
fatigue or corrosion. Here, the decrease in the valve opening
pressure of the score groove portion by the deterioration of the
battery can with the passage of time due to fatigue is caused by a
repetitive variation in inner pressure (repetitive stress) which is
loaded on the battery can over a long period of time (10 to 15
years). In addition, the decrease in the valve opening pressure of
the score groove portion by the deterioration of the battery can
with the passage of time due to corrosion is caused by pitting or
the like of the score groove portion in the anticorrosive plated
steel sheet having a plate layer such as Ni plating.
[0064] The present inventors have carried out the following
examination, and they have found that it is possible to provide a
battery can for a storage battery with a satisfactory score groove
type safety valve.
[0065] First, the present inventors have carried out various
examinations on a cause of a variance in valve opening pressure of
the score groove portion of an individual battery can, and they
have found the following (1-a) to (1-e) with respect to the score
groove portion capable of reducing the variance in the valve
opening pressure.
[0066] (1-a) In a trapezoidal blade edge and a triangular blade
edge, for example, as shown in FIG. 7A, strain is focused on a
local point. Therefore, the shape of the blade edge has a great
effect on the degree and distribution of an amount of process
strain in the vicinity of a score groove bottom portion 5c1
processed by the distal portion of the blade edge. Accordingly, the
degree and distribution of the process strain in the vicinity of
the score groove bottom portion 5c1 greatly vary due to a variance
in the shape of the blade edge (for example, a variance in the
shape of the blade edge for each tool (the blade edge)). As a
result, the valve opening pressure of the score groove portion 5c
of an individual battery can greatly varies.
[0067] Furthermore, the distal portion of the blade edge has a
corner, and thus the blade edge is abraded due to repetitive score
processing, and the shape of the blade edge has a tendency to vary.
Accordingly, due to a variance in the shape of the blade edge, the
valve opening pressure has a tendency to vary.
[0068] In addition, even when the blade edge has an arc shape, when
a radius of curvature R of the score groove bottom portion
(hereinafter, referred to as a radius of curvature R) is 0.20 mm or
less, the blade edge has a tendency to be abraded during the score
processing, and thus the valve opening pressure has a tendency to
vary.
[0069] In addition, when the radius of curvature R exceeds 1.20 mm,
an amount of metal flow, which occurs when a worked portion of the
can is extruded due to the formation of a score groove during the
score processing, increases too much. Accordingly, strain occurs on
a surface which is subjected to the score processing, and thus the
valve opening pressure varies.
[0070] As described above, to sufficiently suppress the variance of
the valve opening pressure, the radius of curvature R is set to be
more than 0.20 mm and equal to or less than 1.20 mm. In addition,
when the radius of curvature R is within a range of more than 0.20
mm and 1.20 mm or less, even when the radius of curvature R of an
inner surface of the can and the radius of curvature R of an outer
surface of the can are not equal to each other, the variance in the
valve opening pressure may be sufficiently suppressed. In a case of
further suppressing the abrasion of the blade edge to further
reliably suppress the variance in the valve opening pressure, it is
preferable that the radius of curvature R be 0.30 mm or more.
[0071] (1-b) From results of comparison between a double-sided
score and a single-sided score, it can be seen that there is a
difference in the variance of the valve opening pressure. In the
double-sided score, the maximum amount of strain in the vicinity of
the score groove bottom portion is reduced, and thus nonuniformity
of the score groove portion may be improved, and the variance in
the valve opening pressure may be sufficiently suppressed. However,
in the single-sided score, the above-described characteristics of
the score groove portion may not be improved, and thus the
suppression of the variance in the valve opening pressure is not
sufficient. Accordingly, in addition to the setting of the radius
of curvature R to more than 0.20 mm and 1.20 mm or less, the score
groove portion is made to be present in both the inner surface and
the outer surface of the can.
[0072] (1-c) Furthermore, for example, as shown in FIG. 7B, when
the radius of curvature R in the double-sided score is set to be
more than 0.20 mm, not only the amount of strain in the vicinity of
the score groove bottom portions 5a1 and 5b1 may be reduced due to
dispersed stress, but also a variation rate (deterioration with the
passage of time) of the radius of curvature R of the blade edge due
to abrasion of the blade edge is suppressed. Accordingly, the
lifespan of the blade edge of a die may be increased. In addition,
when the radius of curvature R exceeds 0.20 mm, since a change of
the valve opening pressure due to a change of the radius of
curvature R is small, a change (variance) of the valve opening
pressure due to the abrasion of the blade edge of the die scarcely
occurs.
[0073] In FIGS. 7A and 7B, to illustrate a stress state in an
easily understandable manner, hatching of a cross-section is
omitted.
[0074] (1-d) In a steel sheet used in the battery can, when the
amount of C is limited to 0.040% by mass or less, the amount of S
is limited to 0.020% by mass or less, and tensile strength TS is
limited to 400 MPa or less, defects inside the steel sheet which
occur due to score processing strain are reduced, and thus a
decrease in ductility of ferrite may be suppressed. Examples of the
defects inside the steel sheet include a cavity that may be formed
at a boundary between Fe.sub.3C and MnS, and ferrite, or a
microcrack that occurs due to a hard characteristic of the steel
sheet itself. In addition, in a steel sheet in which a decrease in
ductility of ferrite due to the score processing is suppressed,
when the radius of curvature R of the double-sided score exceeds
0.20 mm, even when the remaining score thickness d is made as small
as 0.045 mm, stable valve opening pressure may be obtained.
Accordingly, the remaining score thickness d may be made as small
as 0.045 mm. Thus, the battery can is applicable to a use in which
relatively low valve opening pressure is necessary. Particularly,
to obtain more stable valve opening pressure after making the
remaining score thickness d as small as possible, it is preferable
that the radius of curvature R of the double-sided score be 0.30 mm
or more.
[0075] (1-e) On the other hand, in a case of providing a score
groove type safety valve in which the radius of curvature R is 0.30
mm to 1.20 mm, and the remaining score thickness d is 0.055 mm to
0.150 mm, microcracks that occur in the vicinity of the score
groove bottom portion may be greatly reduced. Thereby, when the
score groove portion is formed in such a manner that the radius of
curvature R becomes 0.30 mm or more, and the remaining score
thickness d becomes 0.055 mm or more, with regard to a component
composition of the steel sheet, the amount of C may be reduced to
0.100% by mass or less and the amount of S may be reduced to 0.030%
by mass or less, and with regard to strength characteristics of the
steel sheet, the tensile strength TS may be mitigated to 400 MPa or
less.
[0076] In addition, when the remaining score thickness d exceeds
0.150 mm, the valve opening pressure becomes too high, and thus the
safety valve does not appropriately function as a safety valve of a
storage battery for an industrial use and an in-vehicle use.
[0077] Next, with regard to suppression of a decrease in the valve
opening pressure of the score groove portion by deterioration of
the battery can with the passage of time due to fatigue, the
present inventors have found the following (2-a) to (2-e).
[0078] (2-a) In a score groove portion that is subjected to the
score processing with a trapezoidal blade edge and a triangular
blade edge, inner pressure is repetitively focused on a surface of
the score groove portion, and as a result, fatigue breaking occurs
at low inner pressure. Furthermore, in the case of a trapezoidal
score or a triangular score, since large process strain is applied
to the vicinity of the score groove bottom portion formed by the
blade edge, microcracks occur at the periphery of the inclusions
and the like in the steel sheet, and propagation of fatigue cracks
becomes fast, and thus fatigue-resistant strength greatly
deteriorates. In a score groove portion in which the radius of
curvature R is more than 0.20 mm and equal to or less than 1.20 mm,
stress is not focused too much on a local point of the score groove
portion, and thus the fatigue-resistant strength of the score
groove portion increases, and thus the fatigue breaking is not
likely to occur. Accordingly, to secure very good fatigue-resistant
characteristics against a load caused by a variation of inner
pressure over a long period of time, the radius of curvature R of
the score groove portion is set to be more than 0.20 mm and equal
to or less than 1.20 mm. In a case of further improving the fatigue
resistance, it is preferable that the radius of curvature R be 0.30
mm or more.
[0079] (2-b) In the double-sided score, since severe process strain
is dispersed to both surfaces of the steel sheet during the score
processing, microcracks may be greatly reduced during the score
processing, and thus the fatigue characteristics may be further
improved.
[0080] (2-c) When the radius of curvature R in the double-sided
score is set to be more than 0.20 mm and equal to or less than 1.20
mm, local stress serving as an origin of fatigue is greatly
mitigated, and thus the fatigue resistance is improved.
[0081] (2-d) In a case where the radius of curvature R of the score
groove bottom portion is more than 0.20 mm and equal to or less
than 0.30 mm, and the remaining score thickness d is 0.045 mm to
0.055 mm, when all conditions, in which the amount of C in the
steel sheet is 0.040% by mass or less, the amount of S in the steel
sheet is 0.020% by mass or less, and the tensile strength TS of the
steel sheet is 400 MPa or less, are not satisfied, microcracks that
occur at a boundary between Fe.sub.3C and MnS, and ferrite may not
be reduced. In this case, a fatigue propagation velocity is high,
and fatigue-resistant characteristics deteriorate, and thus the
valve opening pressure of the safety valve decreases along with an
operation time of the battery. Accordingly, in a case where the
radius of curvature R is more than 0.20 mm and equal to or less
than 0.30 mm, and the remaining score thickness is 0.045 mm to
0.055 mm, the amount of C in the steel sheet is limited to 0.040%
by mass or less, the amount of S in the steel sheet is limited to
0.020% by mass or less, and the tensile strength TS of the steel
sheet is limited to 400 MPa or less.
[0082] (2-e) On the other hand, in a case of providing a score
groove type safety valve in which the radius of curvature R is 0.30
mm to 1.20 mm, and the remaining score thickness is 0.055 mm to
0.150 mm, microcracks that occur in the vicinity of the score
groove bottom portion may be greatly reduced. Thereby, when the
score groove portion is formed in such a manner that the radius of
curvature R becomes 0.30 mm or more, and the remaining score
thickness d becomes 0.055 mm or more, with regard to a component
composition of the steel sheet, the amount of C may be reduced to
0.100% by mass or less and the amount of S may be reduced to 0.030%
by mass or less, and with regard to strength characteristics of the
steel sheet, the tensile strength TS may be mitigated to 400 MPa or
less.
[0083] Next, with regard to suppression of a decrease in the valve
opening pressure of the score groove portion by deterioration of
the battery can with the passage of time due to corrosion, the
present inventors have found the following results (3-a) to
(3-c).
[0084] (3-a) In a score groove portion that is subjected to the
score processing with a trapezoidal blade edge and a triangular
blade edge, process strain is focused on a local point of the score
groove portion, and as a result, strong shear strain occurs at a Ni
plate layer, and the Ni plate layer is partially broken due to the
shear strain. Accordingly, pitting progresses from the broken
portion of the Ni plated layer. On the other hand, when using a
circular blade edge capable of forming a score groove portion in
which the radius of curvature R is more than 0.20 mm and is equal
to or less than 1.20 mm, the partial breakage of the plated layer
due to shearing may be suppressed. Accordingly, the decrease in the
valve opening pressure in the Ni plated layer of the score groove
portion due to pitting or the like may be sufficiently
suppressed.
[0085] (3-b) In the double-sided score, an amount of the process
strain of the Ni plated layer is greatly reduced, and thus the
soundness of the Ni plated layer is further improved.
[0086] (3-c) When the radius of curvature R in the double-sided
score is set to be more than 0.20 mm, local strain during the score
processing is mitigated, and thus the soundness of the Ni plated
layer is improved and pitting is suppressed. Accordingly,
satisfactory fatigue resistance may be obtained. Furthermore, when
the radius of curvature R becomes 0.30 mm or more, a safety valve
in which more satisfactory soundness of the Ni plated layer and
more satisfactory fatigue-resistant characteristics are secured may
be obtained.
[0087] In addition, in the battery can for a storage battery, when
a soft stainless steel sheet in which the amount of C is limited to
0.040% by mass or less, the amount of S is limited to 0.020% by
mass or less, and the tensile strength TS is limited to 400 MPa or
less is used for the battery can, it is not necessary to consider
the findings of (3-a) to (3-c). However, in consideration of the
findings of (1-a) to (1-e), and (2-a) to (2-e), a battery can is
configured to be provided with the score groove type safety valve
having the score groove portion, in which the radius of curvature R
is more than 0.20 mm and equal to or less than 1.20 mm, and the
remaining score thickness d is 0.045 mm to 0.150 mm, on both
surfaces of the stainless steel sheet. In this case, it is possible
to provide a battery can for a storage battery in which the local
stress serving as an origin of fatigue is greatly mitigated, and
which is satisfactory in stability of the valve opening pressure,
valve opening characteristics, fatigue resistance, and corrosion
resistance under a harsh environment.
[0088] Here, a portion of the battery can, to which the
double-sided score processing type safety valve is provided, is not
particularly limited, and may be a can lid flat portion (can lid
portion), a can bottom flat portion (can bottom portion), or a can
side wall portion (can body portion) as long as the double-sided
score may be formed.
[0089] FIG. 1 shows a relationship between the radius of curvature
R and the valve opening pressure, and FIG. 2 shows a relationship
between the radius of curvature R and an index of soundness of a Ni
plated layer (average elongation rate of the Ni plated layer). In
FIGS. 1 and 2, characteristics of the safety valve are evaluated by
the following method.
[0090] A Ni plated steel sheet (sheet thickness=0.50 mm) in which
the amount of C is 0.002% by mass, the amount of S is 0.007% by
mass, and the tensile strength TS is 310 MPa is drawn to prepare a
cylindrical can (a can body portion and a can bottom portion). A
score having curvature (roundness) at a front end (score groove
bottom portion) with a score contour .phi. of 25.5 mm is formed in
both a front surface and a rear surface of the can bottom (can
bottom portion) of the cylindrical can to prepare a safety valve in
which the remaining score thickness is 100 .mu.m. Then, a can lid
(can lid portion) is attached to the cylindrical can, and then the
resultant battery can is sealed. Inner pressure is loaded to the
battery can to open the valve, and the relationship between the
radius of curvature R and the valve opening pressure is examined.
In addition, in a case where the radius of curvature R is 0 mm
(that is, a triangular score), elongation of the Ni plated layer is
focused on a local point too much, and thus an average elongation
rate of the Ni plated layer may not be evaluated. Here, the average
elongation rate .DELTA.L of the Ni plated layer is evaluated by the
following expression (Expression 1) after observing a
cross-sectional structure of the score-processed score groove
portion to measure an original line length L0 of the Ni plated
layer which corresponds to the score groove portion before the
score processing, and a line length L1 of the Ni plated layer which
corresponds to the score groove portion after the score
processing.
.DELTA.L=(L1-L0)/L0.times.100 (Expression 1)
[0091] As shown in FIG. 1, when the radius of curvature R is
changed from zero (triangular score) to 0.2 mm, the valve opening
pressure significantly decreases, and when the radius of curvature
R reaches 0.3 mm, the valve opening pressure decreases to the
lowest loaded inner pressure level, and satisfactory valve opening
characteristics may be obtained. When the radius of curvature R is
0.3 mm to 1.0 mm, stable valve opening characteristics at the
minimum valve opening pressure may be obtained, and thus this
radius of curvature R is more preferable. When the radius of
curvature R is 1.0 mm to 1.2 mm, the valve opening pressure
gradually increases along with an increase in the radius of
curvature R, and when the radius of curvature R reaches 1.2 mm, the
valve opening pressure reaches an appropriate limit. When the
radius of curvature R exceeds 1.2 mm, the valve opening pressure
rapidly increases along with an increase in the radius of curvature
R.
[0092] Furthermore, the present inventors have found that a
relationship between the radius of curvature R and the valve
opening pressure as shown in FIG. 1 has the same tendency as a
relationship between the radius of curvature R and stability of the
valve opening pressure, and a relationship between the radius of
curvature R and fatigue strength.
[0093] A relationship between an average elongation rate of the Ni
plated layer and the radius of curvature R, which has a great
effect on the soundness of the Ni plated layer, is shown in FIG. 2.
When the radius of curvature R is within a range of more than 0 and
0.2 mm or less, the average elongation rate of the Ni plated layer
is significantly reduced, and when the radius of curvature R
exceeds 0.2 mm, the average elongation rate of the Ni plated layer
sufficiently decreases, and thus the soundness of the Ni plated
layer may be secured. When the radius of curvature R further
increases, the average elongation rate of the Ni plated layer
gradually decreases, and thus the soundness of the Ni plated layer
is improved. In addition, when the soundness of the Ni plated layer
is improved, the pitting of the Ni plated layer may be decreased,
and thus an abnormal decrease in the valve opening pressure due to
the pitting is not likely to occur. Accordingly, the durability of
the battery can itself is also improved. Also, when the radius of
curvature R is 0.3 mm or more, the average elongation rate of the
Ni plated layer may be reduced by 200% or less, and thus the radius
of curvature R is more preferably 0.3 mm or more.
[0094] Hereinafter, a battery can for a storage battery
(hereinafter, referred to simply as "battery can") according to an
embodiment of the invention will be described in detail. In
addition, in the specification and drawings, the same reference
numerals will be given to components having substantially the same
functional configuration, and a redundant description thereof will
be omitted here.
[0095] FIG. 3A shows a schematic perspective diagram of the battery
can according to the embodiment. As shown in FIG. 3A, the battery
can 1 includes a tubular can body portion 2 having two ends 2a and
2b (a first end 2a and a second end 2b), a can bottom portion 3
that is continuous to the can body portion 2 so as to cover the end
2a of the can body portion 2, and a can lid portion 4. In the
battery can 1, when a battery is assembled, the battery can 1 seal
the battery in such a manner that the can lid portion 4 is provided
to be continuous to the can body portion 2 so as to cover the end
2b of the can body portion 2 as shown in FIG. 3A.
[0096] Besides, as shown in FIG. 3A, the battery can 1 includes a
score groove type safety valve 5 at the can bottom portion 3. In a
case where the battery is configured using the battery can 1, and
pressure inside the battery can 1 is abnormally raised, the safety
valve 5 is opened to prevent the battery can itself from being
ruptured.
[0097] FIG. 4 shows a schematic longitudinal cross-sectional
diagram of the battery can according to the embodiment, which is
cut to pass through the central axis of the battery can 1 shown in
FIG. 3A. Also, FIG. 5A shows a partial schematic diagram
illustrating an enlarged view of broken-line portion A in FIG. 4.
As shown in FIG. 5A, the safety valve 5 is constituted by a score
groove portion 5a (first score groove portion 5a) in an inner
surface of the can bottom portion 3, and a score groove portion 5b
(second score groove portion 5b) in an outer surface of the can
bottom portion 3. In this manner, the safety valve 5 includes the
score groove portions 5a and 5b in the inner surface and the outer
surface of the can bottom portion 3, and the score groove portions
5a and 5b are disposed to be opposite to each other in a
cross-section view in a sheet thickness direction (that is, in a
groove depth direction). In addition, when viewed from a
cross-section that is perpendicular to an extension direction (a
direction perpendicular to a groove width direction and the groove
depth direction) of the score groove portions 5a and 5b, the score
groove portions 5a and 5b have score groove bottom portions 5a1 and
5b1 which have a radius of curvature R. Besides, here, a groove
shape that faces to the extension direction of the score groove
portions 5a and 5b is the same in each case.
[0098] In addition, the can bottom portion 3 provided with the
safety valve 5 (that is, a portion provided with the safety valve)
is formed from a plated steel sheet 3c having a steel sheet portion
3a (an original sheet portion for plating) in which the amount of C
and the amount of S that is an unavoidable impurity are limited,
and which has a tensile strength TS, and plated sheets 3b on a
surface of the steel sheet portion 3a. In this case, the radius of
curvature R and a range of a distance (that is, remaining score
thickness) d between the score groove bottom portions 5a1 and 5b1
are determined in accordance with the amount of C and the amount of
S, and the tensile strength TS of the steel sheet portion 3a.
[0099] With regard to the steel sheet portion 3a of the can bottom
portion 3 which is provided with the safety valve 5, in a case
where the amount of C is limited to 0.040% by mass or less, the
amount of S is limited to 0.020% by mass or less, and the tensile
strength TS is 400 MPa or less, the radius of curvature R is more
than 0.20 mm and equal to or less than 1.20 mm, and preferably 0.30
mm to 1.20 mm. In addition, in this case, the remaining score
thickness d is 0.045 mm to 0.150 mm.
[0100] Here, to secure strength necessary for the battery, for
example, the steel sheet portion 3a may contain 0.0010% to 0.040%
of C. Besides, to reduce the production cost of the plated steel
sheet 3c by reducing the refining cost of the steel sheet portion
3a, the steel sheet portion 3a may contain 0.0005% to 0.020% of
S.
[0101] With regard to the steel sheet portion 3a of the can bottom
portion 3 which is provided with the safety valve 5, in a case
where the amount of C is limited to 0.100% by mass or less, the
amount of S is limited to 0.030% by mass or less, and the tensile
strength TS is 400 MPa or less, the radius of curvature R is more
than 0.30 mm and equal to or less than 1.20 mm. In addition, in
this case, the remaining score thickness d is 0.055 mm to 0.150
mm.
[0102] Here, to secure strength necessary for the battery, for
example, the steel sheet portion 3a may contain 0.0010% to 0.100%
of C. Besides, to reduce the production cost of the plated steel
sheet 3c by reducing the refining cost of the steel sheet portion
3a, the steel sheet portion 3a may contain 0.0005% to 0.030% of
S.
[0103] Also, the lower limit of the tensile strength TS is not
particularly limited as long as the lower limit is a strength
necessary for a battery that is used, but for example, the lower
limit may be 290 MPa.
[0104] Furthermore, to lengthen the lifetime of the battery by
raising the valve opening pressure as long as a safe and stable
battery output is possible even when inner pressure is relatively
increased, it is preferable that the remaining score thickness d be
0.060 mm or more, more preferably 0.080 mm or more or 0.085 mm or
more, and still more preferably 0.090 mm or more or 0.100 mm or
more.
[0105] Besides, to further reduce the cost of the battery can by
further lengthening the lifetime of a blade edge, it is more
preferable that the radius of curvature R be 0.40 mm or more. To
further reliably suppress the process strain that may occur by the
score processing, it is preferable that the radius of curvature R
be 1.00 mm or less.
[0106] For example, in the embodiment, the score groove bottom
portions 5a1 and 5b1 which have the radius of curvature R as shown
in FIGS. 5A and 5B may be provided to the bottoms of the score
groove portions 5a and 5b, respectively. Here, the radius of
curvature R and the remaining score thickness d in FIGS. 5A and 5B
are defined as shown in FIGS. 6A and 6B, respectively. In the score
groove portions 5a and 5b, the score groove bottom portions 5a1 and
5b1 are portions having the radius of curvature R. Accordingly, in
FIG. 5A, the score groove portions 5a and 5b, and the score groove
bottom portions 5a1 and 5b1 are consistent with each other. In FIG.
5B. parts of the score groove portions 5a and 5b correspond to the
score groove bottom portions 5a1 and 5b1. In FIGS. 6A and 6B, to
illustrate each dimension in an easily understandable manner,
hatching of a cross-section is omitted.
[0107] In a case of FIG. 5A, to make the score processing possible,
it is preferable that an angle .alpha. (a value of -90.degree. or
more and less than 90.degree. in which counter-clockwise rotation
with the sheet thickness direction made as a reference is defined
as positive rotation) made by a tangential line of each end of the
score groove bottom portions 5a1 and 5b1 and a sheet thickness
direction (that is, the depth direction of the score groove
portion) of the can bottom portion 3 (that is, a portion of the
battery can 1 which is provided with the safety valve 5) be
0.degree. or more. In addition, in a case of mitigating the process
strain in the vicinity of the score groove portions 5a and 5b as
much as possible, the angle .alpha. is preferably 45.degree. or
less. more preferably 40.degree. or less, and still more preferably
30.degree.. Besides, the score groove shape in FIG. 5A and the
score groove shape in FIG. 5B may be changed in accordance with the
angle .alpha..
[0108] In a case of FIG. 5B, to mitigate the process strain in the
vicinity of the score groove portions 5a and 5b, two remaining
portions (hereinafter, referred to as score groove upper portions
5a2 and 5b2), which are present on both sides of the score groove
bottom portions 5a1 and 5b1, of the score groove portions 5a and 5b
preferably have a predetermined angle in an opening direction of
the score groove portions 5a and 5b. For example, to mitigate the
process strain in the vicinity of the score groove portions 5a and
5b, with regard to the score groove upper portions 5a2 and 5b2 on
one side, an angle .theta.' (hereinafter, referred to as groove
opening degree .theta.') made by a straight line connecting one end
and the other end of the score groove upper portions 5a2 and 5b2,
and a sheet thickness direction (that is, the depth direction of
the score groove portion) of the can bottom portion 3 (that is, a
portion of the battery can 1 which is provided with the safety
valve 5) is preferably 20.degree. or more, and more preferably
22.5.degree. or more. In this case, stress that is applied to the
Ni plating may be dispersed, and thus the soundness of the Ni
plating is improved, and thus the thickness of the Ni plating may
be reduced. In a case where the score groove upper portions 5a2 and
5b2 are present, the groove opening degree .theta.' may be
45.degree. or less or 40.degree. or less to secure continuity
between the score groove bottom portions 5a1 and 5b1, and the score
groove upper portions 5a2 and 5b2.
[0109] In addition, a processing procedure when forming the score
groove portions 5a and 5b in the plated steel sheet 3c is not
particularly limited, but both prior plating and post plating may
be applied to the processing procedure.
[0110] That is, the plated steel sheet (corresponding to the plated
steel sheet 3c) may be directly subjected to the score processing
by a press forming method. In this case, a battery can, which is
satisfactory in stability of the valve opening pressure, valve
opening characteristics, and soundness of the plated layer 3b, may
be provided at a low cost without considering adhesive properties
of the plating in the score processed portions.
[0111] Besides, the plated layer 3b may be formed on a surface of a
steel sheet (corresponding to the steel sheet portion 3a, a steel
sheet for post plating) after the steel sheet is subjected to the
score processing by a press forming method. In this case, a battery
can, which is satisfactory in stability of the valve opening
pressure and the valve opening characteristics, may be provided
without considering deterioration of corrosion resistance due to
the processing.
[0112] Moreover, a soft stainless steel sheet (stainless steel
sheet having tensile strength of 400 MPa or less) may be used in
place of the plated steel sheet 3c. In this case, passivation film
on a surface of the stainless steel sheet has the same function as
the plated layer 3b, and thus it is not necessary for the surface
of the stainless steel sheet to be plated. Accordingly, the
stainless steel sheet may be directly subjected to the score
processing by the press forming method. In this case, a battery
can, which is satisfactory in stability of the valve opening
pressure, valve opening characteristics, and corrosion resistance
under a harsh environment, may be provided without considering
deterioration of corrosion resistance due to processing. In
addition, in a case where the soft stainless steel sheet is used,
an outermost surface on an inner side of the battery can 1 (the can
body portion 2, the can bottom portion 3. and the can lid portion
4) is preferably constituted by the soft stainless steel sheet from
the viewpoint of corrosion resistance.
[0113] Also, the kind of the plated layer 3b is also not
particularly limited, and may be determined in accordance with a
material accommodated in the battery (for example, an electrolytic
solution) or an operating environment of the battery. For example,
it is preferable that the plated layer 3b includes a Ni plated
layer having particularly satisfactory corrosion resistance in an
organic solvent. In this case, a strike plating that improves
plating adhesiveness may be included between the Ni plated layer
and the steel sheet portion 3a, and the Ni plated layer may contain
components of the strike plating. Particularly, in a case where it
is necessary for a surface to have corrosion resistance, or in a
case where it is necessary to avoid mixing of impurities into the
electrolytic solution, it is preferable that the outermost surface
of the plated steel sheet 3c (on an inner side of the battery can 1
(the can body portion 2, the can bottom portion 3, and the can lid
portion 4)) be constituted by the Ni plated layer.
[0114] Here, in a case of applying the Ni plated steel sheet to the
battery can, after Ni plating is performed on a surface of a
cold-rolled steel sheet, annealing is preferably performed for
softening so as to improve workability of the Ni plated layer and
for generation of a Ni--Fe mutual diffusion layer so as to improve
adhesiveness in an interface between the Ni plated layer and the
steel sheet (iron). In addition, the Ni plated steel sheet is not
particularly limited as long as workability during the score
processing is secured, and Ni plating of various alloys such as
Ni--P, Ni--Sn, and Ni--Cu may be applied. That is, the Ni plated
layer or the Ni plated diffusion layer may contain an alloy element
such as P, Sn, and Cu as a selective element. Besides, in a case
where the soft stainless steel sheet is applied to the battery can,
the kind of stainless steel sheet is not particularly limited as
long as the amount of C is 0.040% by mass or less, the amount of S
is 0.020% by mass or less, and the tensile strength TS is 400 MPa
or less. The sheet thickness of the Ni plated steel sheet, the
steel sheet for the post Ni plating, and the soft stainless steel
sheet is not particularly limited, but the sheet thickness may be
0.20 mm to 0.80 mm in consideration of a balance between the
strength and the cost. Particularly, in a case where strength is
necessary, it is preferable that the sheet thickness be 0.30 mm or
more, more preferably 0.35 mm or more or 0.40 mm or more, and still
more preferably 0.45 mm or more. On the other hand, it is
preferable that the sheet thickness be 0.75 mm or less to reduce
the cost as much as possible.
[0115] It is not necessary to limit the above-described production
conditions of the Ni plated steel sheet, the steel sheet for the
post Ni plating, and the soft stainless steel sheet except for the
above component compositions (the amount of C and the amount of S),
and the tensile strength TS as long as these steel sheets are
suitable for drawing of the battery can for a storage battery. In a
case where the Ni plated steel sheet is subjected to the score
processing, the blade edge is smooth, and thus damage to the Ni
plated layer scarcely occurs. However, in this case, since the Ni
plated layer is stretched and becomes thin during the score
processing, the Ni plated layer may be set to be slightly thicker
than necessary. In addition, for example, the thickness (basis
weight) of the plated layer (Ni plated layer) may be controlled to
0.2 .mu.m to 5.0 .mu.m.
[0116] As a modification example of the embodiment, for example,
the battery can may have a structure as shown in FIGS. 3B to
3F.
[0117] That is, as shown in FIGS. 3B and 3D, the battery can 1 may
be provided with the safety valve 5 at the can lid portion 4, and
as shown in FIG. 3E, the battery can 1 may be provided with the
safety valve 5 at the can body portion 2. In addition, the shape of
the battery can 1 is not particularly limited, and the battery can
1 may be a square can as shown in FIGS. 3C to 3E, or may have a
special shape as shown in FIG. 3F. Also, the shape (a shape in a
plan view) of the safety valve 5 which is viewed from an upper side
of the safety valve 5 is not particularly limited, and may be
determined depending on a structure (disposition of a positive
electrode and a negative electrode, and the like) inside the
battery can in a case of constituting a battery. For example, in a
case where the safety valve is provided to the can bottom portion 3
or the can lid portion 4, the safety valve may be disposed in such
a manner that the center of the circular safety valve matches the
center of the can bottom portion 3 or the can lid portion 4 as
shown in FIG. 3A.
[0118] As described above, in the embodiment (including the
modification example), the battery can 1 may be provided with the
safety valve 5 having the score groove portions 5a and 5b in both
of the inner surface and the outer surface (in the inner surface
and the outer surface, respectively) of any one of the can bottom
portion 3, the can body portion 2, and the can lid portion 4.
[0119] In addition, when a positive electrode, a negative
electrode, and an electrolyte (for example, a separator containing
the electrolyte) are accommodated in the battery can 1 according to
the embodiment, a storage battery, which includes the battery can 1
according to the embodiment, the positive electrode, the negative
electrode, and the electrolyte, may be provided.
[0120] Accordingly, the battery can according to the embodiment may
be applied as a battery can for a storage battery in which
satisfactory stability of the valve opening pressure, satisfactory
valve opening characteristics, and satisfactory corrosion
resistance under a harsh environment are necessary. Particularly,
the battery can for a storage battery may be suitably applied as a
battery can for an industrial use (for example, a fixed apparatus),
and an in-vehicle use.
[0121] That is, in the battery can according to the embodiment, a
variance in the valve opening pressure of the score groove portion
of an individual battery can may be reduced. In addition, in the
battery can of the embodiment, a decrease in the valve opening
pressure of the score groove portion by fatigue caused by
repetitive variation of inner pressure (repetitive stress) which is
loaded on the battery can over a long period of time (10 to 15
years) may be almost prevented. Furthermore, in the battery can
according to the embodiment, fracture or cracking of the Ni plated
layer, which accompanies the score processing, scarcely occurs, and
pitting of the score groove portion, and the like may be
suppressed. Accordingly, a decrease in the valve opening pressure
of the score groove portion may be almost prevented.
Examples
[0122] Hereinafter, an effect of the invention will be described
with reference to examples.
[0123] Cast pieces (steel) which contain chemical components shown
in steel A to steel E, and steel G to steel H in Table 1 were
prepared, and hot rolling and cold rolling were performed under
normal conditions to prepare steel sheets (steel). In addition,
with respect to steel sheets other than a soft stainless steel
sheet (steel F). Ni plating was performed before can production or
after can production. In a case where the Ni plating was performed
before the can production (prior plating), Ni plating, annealing,
and temper rolling were performed with respect to the steel sheet
to produce a Ni plated steel sheet, and battery cans (cylindrical
can and square can) were prepared from the Ni plated steel sheet.
On the other hand, in a case where the Ni plating was performed
after the can production (post plating), battery cans were prepared
directly from a steel sheet (raw steel sheet) to which the Ni
plating was not applied. Similarly, a battery can was prepared
directly from a soft stainless steel sheet containing chemical
components shown in steel F. Inner pressure was applied to the
battery cans to evaluate valve opening characteristics of the
respective battery cans. Here. the remainder other than the
chemical components shown in Table 1 includes iron and other
unavoidable impurities.
TABLE-US-00001 TABLE 1 Chemical component (% by mass) TS Steel C Si
Mn P S sol. Al N Ti Nb B (MPa) A 0.035 0.01 0.25 0.008 0.007 0.045
0.0022 -- -- -- 335 B 0.002 0.01 0.10 0.008 0.004 0.035 0.0028
0.015 0.018 0.0003 310 C 0.002 0.01 0.12 0.009 0.015 0.034 0.0022
0.035 0.013 0.0004 307 D 0.005 0.01 0.20 0.007 0.005 0.045 0.0027
Tr. 0.022 Tr. 365 E 0.060 0.01 0.20 0.010 0.022 0.041 0.0032 -- --
-- 330 F C (0.002% by mass) - S (0.007% by mass) - ferrite-based
soft stainless steel 380 G 0.150 0.01 0.15 0.010 0.015 0.045 0.0027
-- 0.018 -- 375 H 0.003 0.80 2.20 0.085 0.010 0.040 0.0020 0.020
0.018 0.0010 410 I 0.002 0.01 0.35 0.011 0.028 0.048 0.0025 0.005
0.025 0.0004 315
[0124] In Table 1, "sol. Al" represents soluble Al. In addition,
"Tr." represents that the amount of a detected chemical component
was small to a degree at which determination of the quantity was
impossible. Also, "-" represents that a chemical component was not
detected during determination.
[0125] In Table 1, test steel A to test steel E, and test steel I
are ultralow-carbon steel, and test steel F is an ultralow
C-ferrite based soft stainless steel sheet which is sold on the
market. In addition, in the steel A, the amount of C is 0.035% by
mass, the amount of S is 0.007% by mass, and the tensile strength
TS is 335 MPa. In the steel B, the amount of C is 0.002% by mass,
the amount of S is 0.004% by mass, and the tensile strength TS is
310 MPa. In the steel C, the amount of C is 0.002% by mass, the
amount of S is 0.015% by mass, and the tensile strength TS is 307
MPa. In the steel D, the amount of C is 0.005% by mass, the amount
of S is 0.005% by mass, and the tensile strength TS is 365 MPa. In
the steel E, the amount of C is 0.060% by mass, the amount of S is
0.022% by mass, and the tensile strength TS is 330 MPa. In the
steel F, the amount of C is 0.002% by mass, the amount of S is
0.007% by mass, and the tensile strength TS is 380 MPa. In the
steel I, the amount of C is 0.002% by mass, the amount of S is
0.028% by mass, and the tensile strength TS is 315 MPa.
[0126] In Table 1, the test steel G and test steel H are high
low-carbon steel, and high-strength steel sheet, respectively. In
the steel G, the amount of C is 0.150% by mass and is more than
0.100% by mass. In the steel H, the tensile strength TS is 410 MPa,
and is more than 400 MPa. Here, an underline in Table 1 represents
that the amount of C, the amount of S, and the tensile strength TS
are not sufficiently limited.
[0127] In addition, in the invention, there is no limitation to the
steel sheets, and it is not necessary to particularly limit other
conditions of the steel sheets as long as conditions in which the
amount of C is 0.100% by mass or less, the amount of S is 0.030% by
mass or less, and the tensile strength TS is 400 MPa or less are
satisfied. Therefore, in the invention, Ni plated steel sheets
which are produced by steel-making, hot rolling, cold rolling, Ni
plating, annealing, and temper rolling which are commonly
performed, steel sheets to which the Ni plating is not applied
(that is, a steel sheet in which the Ni plating is not performed
before can production, and the Ni plating is performed after the
can production), or a soft stainless steel sheet may be applied,
and it is not necessary to particularly regulate a method of
producing a steel sheet.
[0128] Besides, it is not necessary to particularly limit dying
conditions of the battery can, and a dying method thereof, and
normal conditions of producing a battery can for a storage battery
may be applied as long as the radius of curvature R and the
remaining score thickness d can be sufficiently controlled.
[0129] Battery cans provided with a score groove type safety valve
were produced under conditions shown in Table 2 using steel A to
steel I shown in Table 1. Inner pressure was applied to the battery
cans, and as valve opening characteristics, stability of the valve
opening power, valve opening characteristics. and soundness of the
Ni plated layer (excluding post plating and soft stainless steel
sheet) were evaluated. The score groove type safety valve was
provided to a can bottom portion in circular cans of test Nos. 1 to
22, and 25 to 28, a can lid portion in the square can of test No.
23, and a can side wall portion (can body portion) in the square
can of test No. 24, respectively. In test Nos. 1 to 26, the safety
valve was a double-sided score, and in test Nos. 27 and 28, the
safety valve was a single-sided score.
[0130] A variance in a can opening time when the number of cycles n
during charging and discharging was increased, deterioration of
fatigue strength when repetitive inner pressure was loaded, an
extent of an effect on valve opening characteristics by abrasion of
a die, and the like were comprehensively evaluated, and stability
of the valve opening power was evaluated by three grades including
not good (NG in Table 2), good (G in Table 2), and very good (VG in
Table 2).
[0131] Valve opening pressure that is necessary when the battery
can is applied for an industrial use and an in-vehicle use was
comprehensively evaluated, the valve opening characteristics being
evaluated by three grades including not good (NG in Table 2), good
(G in Table 2), and very good (VG in Table 2).
[0132] A degree of damage of the plated layer of the score groove
portion was evaluated by SEM (scanning electron microscopy), EPMA
(electron probe X-ray microanalysis), and the like, and the
soundness of the Ni plated layer was evaluated by three grades
including not good (NG in Table 2), good (G in Table 2), and very
good (VG in Table 2). However, in sample Nos. 12, 18, and 26, post
plating was performed, and thus evaluation was not performed ("-"
in Table 2). In addition, in sample No. 19, a soft stainless steel
sheet was used, and thus evaluation was not performed ("-" in Table
2).
TABLE-US-00002 TABLE 2 Dimensions of battery Evaluation result *2
Ni plating can Score shape of safety valve Valve Outer/ Can Shape
of distal Distal Remaining opening Test Kind of Inner .phi. height
Contour end inner/ end thickness Sta- charac- Sound- No. Steel
plating .mu.m Shape mm mm mm outer mm .theta..degree. .mu.m bility
teristic ness Remarks 1 A Prior plating 2/2 Circular 40 115
.phi.25.5 Trapezoidal 60 50 NG G NG Conventional 0.3 W/0.3 W
Example 2 B Prior plating 2/2 Circular 40 115 .phi.25.5 Trapezoidal
60 50 NG G NG Conventional 0.3 W/0.3 W Example 3 B Prior plating
2/2 Circular 40 115 .phi.25.5 Triangular 60 50 NG G NG Conventional
0 R/0 R Example 4 B Prior plating 2/2 Circular 40 115 .phi.25.5
0.15 R/0.15 R 60 50 NG G NG Comparative Example 5 A Prior plating
2/2 Circular 40 115 .phi.25.5 0.50 R/0.50 R 60 50 G G G Example 6 B
Prior plating 2/2 Circular 40 115 .phi.25.5 0.25 R/0.25 R 60 50 G G
G Example 7 B Prior plating 2/2 Circular 40 115 .phi.25.5 0.50
R/0.50 R 60 45 G VG G Example 8 B Prior plating 2/2 Circular 40 115
.phi.25.5 0.50 R/0.50 R 60 50 VG VG G Example 9 B Prior plating 2/2
Circular 40 115 .phi.25.5 0.50 R/0.50 R 60 140 VG G VG Example 10 B
Prior plating 2/2 Circular 40 115 .phi.25.5 0.65 R/0.65 R 60 60 VG
VG VG Example 11 B Prior plating 2/2 Circular 40 115 .phi.25.5 0.80
R/0.80 R 60 60 VG VG VG Example 12 B Post plating 2/2 Circular 40
115 .phi.25.5 0.50 R/0.50 R 60 60 VG VG -- Example 13 B Prior
plating 2/2 Circular 40 115 .phi.25.5 1.50 R/1.50 R 60 60 NG NG VG
Comparative Example 14 B Prior plating 2/2 Circular 40 115
.phi.25.5 0.50 R/0.50 R 60 30 NG VG NG Comparative Example 15 C
Prior plating 2/2 Circular 40 115 .phi.25.5 0.50 R/0.50 R 60 80 VG
VG VG Example 16 D Prior plating 2/2 Circular 40 115 .phi.25.5 0.50
R/0.50 R 60 80 VG VG VG Example 17 E Prior plating 2/2 Circular 40
115 .phi.25.5 0.50 R/0.50 R 60 70 VG VG VG Example 18 E Post
plating 2/2 Circular 40 115 .phi.25.5 0.50 R/0.50 R 60 60 VG VG --
Example 19 F None 2/2 Circular 40 115 .phi.25.5 0.50 R/0.50 R 60 60
VG VG -- Example 20 G Prior plating 2/2 Circular 40 115 .phi.25.5
0.50 R/0.50 R 60 50 NG VG NG Comparative Example 21 H Prior plating
2/2 Circular 40 115 .phi.25.5 0.50 R/0.50 R 60 50 NG NG NG
Comparative Example 22 I Prior plating 2/2 Circular 40 115
.phi.25.5 0.50 R/0.50 R 60 50 NG G G Comparative Example 23 B Prior
plating 2/2 Square *1 130 .phi.25.5 0.50 R/0.50 R 60 60 VG VG VG
Example 24 B Prior plating 2/2 Square *1 130 .phi.25.5 0.50 R/0.50
R 60 60 VG VG VG Example 25 B Prior plating 2/2 Circular 40 115
.phi.25.5 0.50 R/0.80 R 60 60 VG VG VG Example 26 B Post plating
2/2 Circular 40 115 .phi.25.5 0.60 R/0.90 R 60 60 VG VG -- Example
27 B Prior plating 2/2 Circular 40 115 .phi.25.5 Flat/ 60 50 NG NG
NG Conventional trapezoidal Example 0.3 W 28 B Prior plating 2/2
Circular 40 115 .phi.25.5 Flat/ 60 50 NG G NG Conventional
triangular 0 R Example *1 Length of short side .times. Length of
long side: 40 mm .times. 100 mm. *2 NG: Not Good, G: Good, VG: Very
Good.
[0133] In test No. 1, a cross-sectional shape of the score groove
of the safety valve was a trapezoidal shape, and a lower width of
the score groove was 0.3 mm (0.3 W). Also, in test No. 2, a
cross-sectional shape of the score groove of the safety valve was a
trapezoidal shape, and a lower width of the score groove was 0.3 mm
(0.3 W). In test No. 3, a cross-sectional shape of the score groove
of the safety valve was a triangular shape, and a lower width of
the score groove was 0 mm. These test Nos. 1, 2, and 3 were
double-sided scores of a score groove type in the related art, and
the stability of the valve opening power and the soundness of the
Ni plated layer were evaluated as failure (NG).
[0134] In test No. 4, the radius of curvature R of the score groove
bottom portion was 0.15 mm (that is, 0.20 mm or less), and thus the
stability of the valve opening characteristics and the soundness of
the Ni plated layer were not sufficient (NG).
[0135] In test No. 5, a Ni plated steel sheet of the steel A in
which the amount of C was 0.035% by mass, and the amount of S was
0.007% by mass was used as a test steel sheet, the radius of
curvature R of the score groove bottom portion was 0.50 mm, and the
remaining score thickness d was 50 .mu.m, and thus the stability of
the valve opening characteristics, the valve opening
characteristics, and the soundness of the Ni plated layer were good
(G).
[0136] In test Nos. 6, 7, 8, 9, 10, and 11, a Ni plated steel sheet
of the steel B in which the amount of C was 0.002% by mass, and the
amount of S was 0.004% by mass was used as a test steel sheet, the
radius of curvature R of the score groove bottom portion was 0.25
mm to 0.80 mm, and the remaining score thickness d was 45 .mu.m to
140 .mu.m, and thus in Nos. 6, 7, 8, and 9, the stability of the
valve opening power, the valve opening characteristics, and the
soundness of the Ni plated layer were good (G) or very good (VG).
In Nos. 10 and 11, all of the stability of the valve opening power,
the valve opening characteristics, and the soundness of the Ni
plated layer were very good (VG).
[0137] In test No. 12, a steel sheet for post plating of the steel
B in which the amount of C was 0.002% by mass, and the amount of S
was 0.004% by mass was used as a test steel sheet, the radius of
curvature R of the score groove bottom portion was 0.50 mm, and the
remaining score thickness d was 60 .mu.m, and thus the stability of
the valve opening power and the valve opening characteristics were
very good (VG), and the corrosion resistance was also secured by a
post plating treatment.
[0138] In test Nos. 13 and 14, a Ni plated steel sheet of the steel
B in which the amount of C was 0.002% by mass, and the amount of S
was 0.004% by mass was used as a test steel sheet. Among these, in
test No. 13, since the radius of curvature R of the score groove
bottom portion was 1.50 mm (that is, 1.20 mm or more), the
stability of the valve opening power, and the valve opening
pressure were not good (NG). In test No. 14, since the remaining
score thickness d was 30 .mu.m, the stability of the valve opening
power and the soundness of the Ni plated layer were not good
(NG).
[0139] In test No. 15, a Ni plated steel sheet of the steel C in
which the amount of C was 0.002% by mass, and the amount of S was
0.015% by mass was used as a test steel sheet, the radius of
curvature R of the score groove bottom portion was 0.50 mm, and the
remaining score thickness d was 80 .mu.m, and thus the stability of
the valve opening power, the valve opening characteristics, and the
soundness of the Ni plated layer were very good (VG).
[0140] In test No. 16, a Ni plated steel sheet of the steel D in
which the amount of C was 0.005% by mass, and the amount of S was
0.005% by mass was used as a test steel sheet, the radius of
curvature R of the score groove bottom portion was 0.50 mm, and the
remaining score thickness d was 80 .mu.m, and thus the stability of
the valve opening power, the valve opening characteristics, and the
soundness of the Ni plated layer were very good (VG).
[0141] In test No. 17, a Ni plated steel sheet of the steel E in
which the amount of C was 0.060% by mass, and the amount of S was
0.022% by mass was used as a test steel sheet, the radius of
curvature R of the score groove bottom portion was 0.50 mm, and the
remaining score thickness d was 70 .mu.m, and thus the stability of
the valve opening power, the valve opening characteristics, and the
soundness of the Ni plated layer were very good (VG).
[0142] In test No. 18, a Ni plated steel sheet of the steel E in
which the amount of C was 0.060% by mass, and the amount of S was
0.022% by mass was used as a test steel sheet, the radius of
curvature R of the score groove bottom portion was 0.50 mm, and the
remaining score thickness d was 60 .mu.m, and thus the stability of
the valve opening power, the valve opening characteristics, and the
soundness of the Ni plated layer were very good (VG).
[0143] In test No. 19, a ferrite-based low C stainless steel sheet
in which the tensile strength TS was 380 MPa, the amount of C was
0.002% by mass, and the amount of S was 0.007% by mass was used as
a test steel sheet, the radius of curvature R of the score groove
bottom portion was 0.50 mm, and the remaining score thickness d was
60 mm, and thus the stability of the valve opening power, and the
valve opening characteristics were very good (VG).
[0144] In test No. 20, a Ni plated steel sheet of the steel G in
which the amount of C was 0.150% by mass (that is, more than 0.100%
by mass) was used as a test steel sheet, and thus the stability of
the valve opening power and the soundness of the Ni plated layer
were not good (NG). In test No. 21, a Ni plated steel sheet of the
steel H in which the amount of C was 0.003% by mass, and the amount
of S was 0.010% by mass, but the tensile strength TS was 410 MPa
(that is, more than 400 MPa) was used as a test steel sheet, and
thus the stability of the valve opening power, valve opening
characteristics, and the soundness of the Ni plated layer were not
good (NG). In test No. 22, a Ni plated steel sheet of the steel I
in which the amount of C was 0.002% by mass, the amount of S was
0.028% by mass, and the tensile strength TS was 315 MPa was used as
a test steel sheet, but the remaining score thickness d was 50
.mu.m with respect to a relatively high amount of S (0.020% to
0.030%), and thus the stability of the valve opening power was not
good (NG).
[0145] In test Nos. 23 and 24, large-sized square battery cans of
40 mm.times.100 mm.times.130 mm (height) were prepared using a Ni
plated steel sheet of the steel B in which the amount of C was
0.002% by mass, and the amount of S was 0.004% by mass as a test
steel sheet, and a safety valve in which the radius of curvature R
of the score groove bottom was 0.50 mm and the remaining score
thickness d was 60 .mu.m was provided to the large-sized battery
cans. The safety valve was provided to a can lid portion in No. 23,
and a can side wall portion (can body portion) in No. 24. In Nos.
23 and 24, the stability of the valve opening power, the valve
opening characteristics, and the soundness of the Ni plated layer
were very good (VG).
[0146] In test No. 25, a Ni plated steel sheet of the steel B in
which the amount of C was 0.002% by mass, and the amount of S was
0.004% by mass was used as a test steel sheet, the radius of
curvature R of the score groove in an inner surface of the can was
0.50 mm, the radius of curvature R of the score groove in an outer
surface of the can was 0.80 mm, and the remaining score thickness d
was 60 .mu.m. In the test No. 25, the radii of curvature R of the
score grooves in the inner and outer surfaces of the can were
different from each other, but the stability of the valve opening
power, the valve opening characteristics, and the soundness of the
Ni plated layer were very good (VG).
[0147] In test No. 26, a steel sheet for post plating of the steel
B in which the amount of C was 0.002% by mass, and the amount of S
was 0.004% by mass was used as a test steel sheet, the radius of
curvature R of the score groove in an inner surface of the can was
0.60 mm, the radius of curvature R of the score groove in an outer
surface of the can was 0.90 mm, and the remaining score thickness d
was 60 .mu.m. In test No. 26, the radii of curvature R of the score
grooves in the inner and outer surfaces of the can were also
different from each other, but the stability of the valve opening
power and the valve opening characteristics were very good (VG),
and the corrosion resistance was also secured by a post plating
treatment.
[0148] In test No. 27, a cross-sectional shape of the score groove
of the safety valve was a trapezoidal shape, and a lower width of
the score groove was 0.3 mm (0.3 W). In test No. 28, a
cross-sectional shape of the score groove of the safety valve was a
triangular shape, and a lower width of the score groove was 0 mm.
These test Nos. 27 and 28 were single-sided scores of a score
groove type in the related art, and the stability of the valve
opening pressure and the soundness of the Ni plated layer were
evaluated as failure (NG).
[0149] In addition, in these test Nos. 27 and 28, the score groove
was formed only in the outer surface of the can, and the inner
surface (a surface opposite to the score groove) of the can had a
flat shape. Also, in test Nos. 27 and 28, a Ni plated steel sheet
of the steel B in which the tensile strength TS was 310 MPa, the
amount of C was 0.002% by mass, and the amount of S was 0.004% by
mass was used as a test steel sheet.
[0150] In addition, distal end .theta. in Table 2 is an angle made
by two portions (extension lines of these two portions) of a die
which correspond to score groove upper portions, and in a score
groove portion having score groove upper portions as shown in FIG.
5B, the groove opening degree .theta.' corresponds to 0.5 times of
the distal end .theta..
[0151] As is clear from the above-described results, in the battery
can for a storage battery which is provided with the score groove
type safety valve according to the invention, a variance in the
valve opening pressure of the score groove portion of an individual
battery can is small, and the valve opening pressure of the score
groove portion scarcely decreases by deterioration of the battery
can with the passage of time (for example, 10 to 15 years) due to
fatigue or corrosion. Accordingly, even when inner pressure is
repetitively loaded on the battery can over a long period of time
(10 to 15 years), in the battery can for a storage battery which is
provided with the score groove type safety valve according to the
invention, the valve opening pressure scarcely decreases due to
fatigue of the score groove portion. In addition, even when the
prior plating is performed, in the battery can for a storage
battery which is provided with the score groove type safety valve
according to the invention, the valve opening pressure scarcely
decreases due to pitting of the score groove portion.
[0152] Hereinbefore, the preferred examples of the invention have
been described, but the invention is not limited to these examples.
Addition, omission, substitution, and other modifications of
configuration may be made within a range not departing from the
gist of the present invention. The present invention is not limited
by the above-described description, and is limited only by the
attached claims.
INDUSTRIAL APPLICABILITY
[0153] It is possible to provide a battery can for a storage
battery which is provided with a score groove type safety valve in
which a variance in valve opening pressure of a score groove
portion of an individual battery can is small, and valve opening
pressure of the score groove portion scarcely decreases by
deterioration of the battery can with the passage of time due to
fatigue or corrosion.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
[0154] 1: BATTERY CAN (BATTERY CAN FOR STORAGE BATTERY) [0155] 2:
CAN BODY PORTION (CAN SIDE-WALL PORTION) [0156] 2a: END (FIRST END)
[0157] 2b: END (SECOND END) [0158] 3: CAN BOTTOM PORTION (CAN
BOTTOM) [0159] 3a: STEEL SHEET PORTION (STEEL SHEET) [0160] 3b:
PLATED LAYER (PLATING) [0161] 3c: PLATED STEEL SHEET [0162] 4: CAN
LID PORTION (CAN LID) [0163] 5: SAFETY VALVE [0164] 5a, 5b: SCORE
GROOVE PORTION [0165] 5a1, 5b1: SCORE GROOVE BOTTOM PORTION [0166]
5a2, 5b2: SCORE GROOVE UPPER PORTION [0167] R: RADIUS OF CURVATURE
[0168] d: REMAINING SCORE THICKNESS [0169] .theta.': GROOVE OPENING
DEGREE
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